The present invention relates to system for detection of the position of electrodes of a defibrillator or a training defibrillator on a training manikin.
For years, the use of defibrillators in the case of sudden cardiac arrest has been recognized as the only curative treatment. Defibrillation involves the discharge of an electric pulse with relatively high energy through electrodes connected to the patient's chest. Several designs of electrodes exist, but generally they can be divided into two groups: "Paddles" are electrodes that are held manually on the chest. Adhesive electrodes or "pads" are electrodes that are fixed to the chest by the use of a conducting adhesive.
The electrodes are used both to discharge the electrical shock, to measure the patient's ECG, and to measure any impedance.
Defibrillation may, by its very nature, involve a risk for those who treat the patient, if they touch the patient or in any other way come into contact with the electrodes.
Traditionally, highly trained personnel in hospitals have carried out defibrillation. However, defibrillators have become much easier to use over the last ten years, and thus have also come to be used outside of the hospitals, primarily by the ambulance services. There is also a clear tendency for defibrillators to be used by the laity before the ambulance reaches the patient.
This means that there is a great need for training the users of defibrillators. Such training systems are available, and mainly consist of a training doll (manikin) and an electronic simulator. The defibrillator patient cable is connected to contact points on the chest of the training manikin, and the simulator simulates typical heart rhythms, in addition to handling and registering the electric shock. The manikin and/or defibrillator may also contain a report generator, which registers and reports the treatment that is being carried out.
In this training system, the connection of the electrode takes place through galvanic coupling between the manikin and the defibrillator, normally without the use of defibrillation electrodes. The ECG signal that is generated by the simulator is transmitted to the defibrillator through the electrode connections, and the electric shock being discharged from the defibrillator is transmitted the other way, to the manikin. The connections on the manikin must then have a typical patient impedance of approximately 50 Ohm, which must be able to absorb the relatively high energy from the defibrillator. Beyond this, there is no direct communication between the manikin and the defibrillator.
This has several disadvantages: Visible contact points are used for connecting the defibrillator. This means that there is no opportunity for practicing realistic placement of electrodes based on anatomical references, or for practicing the manipulation that is required for effective connection and placement of the electrodes.
When the defibrillator is used, it will normally give off an energy pulse of between 200 Joules and 360 Joules. The disadvantage of this is that the electronics in the manikin must handle both high voltages and high effects, which makes the solution both large and costly. A further disadvantage is the fact that students may be exposed to high voltages, something that constitutes a safety risk. The fact that the energy is drawn from the defibrillator battery is another disadvantage, as more and more defibrillators are equipped with expensive, non-rechargeable primary batteries based on lithium.
There are training defibrillators available that do not have the disadvantages of high voltage and expensive lithium batteries. These devices, however, do not interact with the manikin, and will operate in the same manner whether the electrodes are connected to the manikin or not.
Defibrillators that can run their own training software are also available. In this mode, the defibrillator will not use the high voltage system, instead it will simulate the discharge of electric shocks and the measurements of the electrical activity of the heart. These devices also have no interaction with the manikin, and will operate in the same manner whether the electrodes are connected to the manikin or not.
It is essential to patient treatment that the electrodes be placed in the correct position on the patient, so as to deliver sufficient energy to the heart muscle. This correct emplacement is dependent on the user having been trained correctly, e.g. by practicing on a manikin.